Answer: Most likely the industrial revolution.
Explanation: The use of machines in production became more and more prevalent, eventually many factories were built in cities which caused pollution therefore making the air gross.
Early Trade. The first Europeans to purchase furs from Indians wereFrench and English fishermen who, during the 1500s, fished off the coast of northeastern Canada and occasionally traded with the Indians. In exchange, the Indians received European-manufactured goods such as guns, metal cooking utensils, and cloth.
A job, they left the countryside and migrated to cities and towns for new jobs.
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